The present invention can be best understood and appreciated by undertaking a brief review of the crude oil distillation process, and most particularly, the role delayed coking plays within that process.
In its unrefined state, crude oil is of little use. In essence, crude oil (a.k.a. hydrocarbon) is a complex chemical compound consisting of numerous elements and can. Such impurities can include, but are not limited to sulfur, oxygen, nitrogen and various metals that must be removed during the refining process.
Refining is the separation and reformation of a complex chemical compound into desired hydrocarbon products. Such product separation is possible as each of the hundreds of hydrocarbons comprising crude oil possess an individual boiling point. During refining, or distillation, crude oil feedstock temperature is raised to a point where boiling begins (a.k.a. "initial boiling point, or "IBP") and continues as the temperature is increased. As the boiling temperature increases, the butane and lighter fraction of crude oil are first distilled. Such distillation begins at IBP and terminates slightly below 100.degree. F. The fractions boiling through this range are represented and referred to as the "butanes and lighter cut."
The next fraction, or cut, begins slightly under 100.degree. F. and terminates at approximately 220.degree. F. This fraction is represented and referred to as straight run gasoline. Then, beginning at 220.degree. F. and continuing to about 320.degree. F. the Naphtha cut occurs, and is followed by the kerosene and gas/oil cuts, occurring between 320.degree. F. and 400.degree. F., and 450.degree. F. to 800.degree. F., respectfully. A term-of-art "residue cut" includes everything boiling above 800.degree. F.
The residue cut possesses comparatively large volumes of heavy materials and two fundamental processes are employed to convert appreciable amounts of such residuals to lighter materials--thermal cracking and delayed coking. While thermal-cracking may be properly considered "the use of heat to split heavy hydrocarbon into its lighter constituent components," delayed coking should be considered "severe thermal cracking" and occurs within a coke drum after a coker feedstock has been heated in an apparatus referred to as a coking heater, or "delayed coker charge heater." An improved delayed coker charge heater and process serve as the focus of the instant invention.
Delayed coking processes and heaters are well known in the art and have been discussed and disclosed, for example, in U.S. Pat. No. 5,078,857, invented by M. Shannon Melton and issued Jan. 7, 1992 (hereafter referred to as "Melton"). Melton and prior art references cited herein are hereby provided to disclose and distinguish said art from the novel improvements embodied and afforded by the instant invention.
Today, delayed coker charge heaters are required to address service demands far more severe than in times past. Such demands typically include reduced recycling rates, heavier processing fluids (a.k.a. "coker feedstock"), and increases in undesirable processing fluid components, such as, but not limited to, asphaltine content, inerts, metals, salts, etc. Increased fresh feed charge rates and the afore stated demands result in a commensurate increase in fouling/coking rates within the interior portions of a coker heater's processing coil or heating conduit. Increased fouling rates, in turn, increase occurrences of coker "down time" to decoke fouled processing coils. Coker charge heaters as represented within the present art have failed to adequately address the afore stated problems. The present invention, by disclosing a novel and unique processing design and methodology, addresses such increased service demands and obviates many of the deficiencies represented in the present art.
Accordingly, the present invention is directed to an improved process and article of manufacture to advance the performance efficiency and life cycle of delayed coker charge heaters by introducing coker feedstock to the lower portion of a delayed coker charge heater and "upflowing" such feedstock to an exiting capability located in the generally upper portion of said coker charge heater's radiant heating section.